An experimental set of small Pelican plugins to add Jekyl-style enhancements to markdown

enhanced_markdown.py

import warnings
import re
import itertools

from pelican.readers import MarkdownReader, EXTENSIONS
from pelican.utils import pelican_open
from pelican import signals


def split_args(argstring):
    """Split on spaces, correctly handling single and double quotes"""
    args = re.split(''' (?=(?:[^'"]|'[^']*'|"[^"]*")*$)''', argstring)

    R = re.compile("""(^".*"$)|(^'.*'$)""")
    def strip_quotes(arg):
        return arg[1:-1] if R.match(arg) else arg

    return filter(strip_quotes, args)


class EnhancedMarkdownReader(MarkdownReader):
    include_tags = {}
    
    @classmethod
    def register_tag(cls, tag, tag_func):
        """Register a new enhanced markdown tag."""
        if tag in cls.include_tags:
            warnings.warn("Enhanced Markdown: overriding tag '%s'" % tag)
        cls.include_tags[tag] = tag_func

    def read(self, source_path):
        """Parse content and metadata of markdown files"""
        R = re.compile('\{%.*%\}')
        with pelican_open(source_path) as text:
            includes = [pattern.group() for pattern in R.finditer(text)]

            # process all includes
            for i in range(len(includes)):
                args = split_args(includes[i][2:-2])
                func = self.include_tags.get(args[0])
                if func is not None:                    
                    includes[i] = func(*args[1:])

            # add an empty string to includes so that chaining works
            includes.append('')

            # reconstruct string
            text = ''.join(itertools.chain(*zip(R.split(text), includes)))

        content = self._md.convert(text)
        metadata = self._parse_metadata(self._md.Meta)
        return content, metadata


def replace_reader(gen):
    for ext in EnhancedMarkdownReader.file_extensions:
        EXTENSIONS[ext] = EnhancedMarkdownReader
 
 
def register():
    signals.initialized.connect(replace_reader)

image_tag.py

"""
Pelican plugin which allows inclusion of images.

Example:

{% img filename.png [width height] %}
"""
import os
from enhanced_markdown import EnhancedMarkdownReader, register


def image_tag(*args):
    filename = args[0]
    image_url = os.path.join('/static/images/', filename)
    ret =  '<img src="%s"' % image_url

    try:
        width = args[1]
        ret += ' width="%s"' % width
    except IndexError:
        pass

    try:
        height = args[2]
        ret += ' height="%s"' % height
    except IndexError:
        pass

    ret += ">\n"

    return ret


EnhancedMarkdownReader.register_tag('img', image_tag)

include_code.py

"""
Pelican plugin which allows include of code blocks.

Example:

{% include_code my_script.py %}
"""
import os
from enhanced_markdown import EnhancedMarkdownReader, register


def include_code(*args):
    filename = args[0]

    # TODO: allow code directory to be specified in configuration
    code_url = os.path.join('/static/code/', filename)
    code_path = os.path.join('content', 'code', filename)
    if not os.path.exists(code_path):
        raise ValueError("path %s does not exist" % code_path)

    # TODO: allow more than just python code
    s = '\n``` python\n'
    with open(code_path) as code:
        s += ''.join(code)
    s += '\n```\n[(download code)](%s)\n' % code_url
    return s


EnhancedMarkdownReader.register_tag('include_code', include_code)

video_tag.py

"""
Pelican plugin which allows inclusion of videos.

Example:

{% video url/to/video [width height] [url/to/poster] %}
"""
import os
from enhanced_markdown import EnhancedMarkdownReader, register


def video_tag(*args):
    video_url = args[0]
    ret =  '<video'

    try:
        width = args[1]
        ret += ' width="%s"' % width
    except IndexError:
        pass

    try:
        height = args[2]
        ret += ' height="%s"' % height
    except IndexError:
        pass

    ret += ' preload="none" controls'

    try:
        poster_url = args[3]
        ret += ' poster="%s"' % poster_url
    except IndexError:
        pass

    ret += ">\n"
    ret += '   <source src="%s" type="video/mp4; codecs=\'avc1.42E01E, mp4a.40.2\'">\n</video>\n' % video_url

    return ret


EnhancedMarkdownReader.register_tag('video', video_tag)